The aim of this research is to gain detailed information about the structure of several membrane transport systems. In particular I intend to test two hypotheses: 1) transport involves movement of ions only short distances between specific sites approachable from opposite sides of the membrane and 2) transport requires a dimer (or larger oligomer) of interacting subunits. The human erythrocyte anion transport system (passive) and the dog kidney (Na,K)-ATPase (active transport) will be used for initial studies. The distance between ion and effector binding sites approachable from opposite sides of the membrane will be measured by the method of fluorescence resonance energy transfer. Other fluorescence techniques will be used to investigate the effects of protein associations, subunit dissociations, detergent solubilization, and proteolytic cleavage on the integrity of these systems as judged by ligand binding ability and partial reactions. The predictions made from studies of these systems will be tested in other transport systems (i.e., (Ca,K)-ATPase and coupling factors).